1. Field of the Invention
This invention generally relates to mechanically fastened belt splices for agricultural machinery belts. The invention more particularly concerns mechanical splices which help to prolong the operational lives of the belts, and to methods of making such splices.
2. Description of the Prior Art
Belting is used today in many types of agricultural machinery, e.g., hay balers. A popular type of hay baler which is marketed today employs a plurality of belts which are used to form the hay into round bales. This type of baler is known as a round hay baler. The belts which are used on the round hay balers are typically in the order of 40 feet long and of the type described in commonly assigned patents U.S. Pat. No. 4,371,580 and U.S. Pat. No. 4,900,609, which are incorporated herein by reference.
There are several factors which must be taken into consideration when designing belting for hay balers. One factor is that when a hay baler is making bales, the belts are subjected to heavy loads. These loads cause the belts to stretch, and the amount that a belt stretches under the load must remain within a certain tolerance; otherwise, the bale it is making will become too large, thereby interfering with proper baler operation.
Manufacturers of hay balers have continued to increase the specification for the density of bales which a baler can produce. The amount of loading to which the belts of a baler are thereby subjected is increased, and hence the likelihood that a belt will stretch beyond tolerable limits for proper operation is increased. When a belt stretches beyond tolerable limits, the belt is generally removed and shortened. Shortening the belt is typically accomplished by trial and error techniques, especially in the fields. Such trial and error techniques are time consuming and can produce unsatisfactory results.
The two most common splices are vulcanized splices and mechanical splices. The underlying principle in vulcanized splicing is the establishment of adhesion between the components of the two belt ends being joined together in the splices. The goal is to develop adhesion in the splices equal to that in the original belt. In mechanical splices, the ends of the belt are connected by a mechanical device such as the "clipper splice" that is illustrated in FIG. 2.
Another factor to be considered in the design of belt splices is the ability of the belt to flex in operation without damaging the splice. In that regard, a typical round hay baler employs a plurality of rollers on which the belts are installed. The position of the rollers is such that the belts are subjected to a substantial amount of flexing in traveling around the rollers. Moreover, some of the rollers are positioned such that the belts must travel in an S-shape during operation. If a belt fails due to the flexing stress, the belt must be replaced to obtain proper operation of the baler. The typical failure point, particularly when mechanical splices are used, is at the point of splice.
Other factors when considering the type of splice to employ are cost and ease of installation. Although vulcanized splices are generally more durable than mechanical splices, they typically cost at least twice as much and they are much more difficult to install, particularly in the field.
Belts used in agricultural applications are most commonly fastened with mechanical splices. The mechanical splices, however, tend to deteriorate rapidly in operation and require substantial maintenance.
Belt slippage and mistracking are caused by a number of factors. In dry and dusty conditions, the dry crop and soil residue are deposited on the belt surfaces and roller surfaces. The residue acts as a lubricant causing both slippage and mistracking. In wet and slippery conditions, such as when baling wet hay or chopped silage, excess moisture also acts as a lubricant causing slippage and mistracking. Also, some crops, such as silage, leave a sticky residue on the belts which causes crop material to adhere to the belt surface. This causes the belts to react unevenly at the rollers, again causing slippage and mistracking. During slippage and mistracking, the belts may contact fixed guides, the belts may roll over, and adjacent belts may rub together. These occurrences damage the belt edges and the ends of the mechanical fasteners.
Mechanical methods have been employed in an effort to overcome the slippage and crop material collection problems, but with minimal success and often to the detriment of the mechanical fastening system. One such method has been to weld metal flighting, such as auger flighting, in a spiral configuration axially along a steel roller surface. The intent is for the flighting to scrape off crop material collecting on the belt surface. While the flighting does scrape the belt surface, it also scrapes the mechanical fastener. Many times the fastener is scraped from the belt.
Rigid and stationary belt dividers and guides are also employed to prevent mistracking. However, as the lateral edges of the belts contact the guides, the ends of the mechanical fasteners become damaged.
The combination of crop conditions, built-in metal or rubber rollers, belt guides and other components that physically scrape the belt all result in increased stresses and strains at the fastened area of the joined belt ends. Mechanical fasteners transfer these stresses and strains to the belt reinforcing fibers through the area of belt carcass penetration and by the member of the fastener that actually penetrates the belt carcass. There is a constant variable of stress and strain from one point to another point along the cross-sectional plane of the belt and the fastener area. There is also a belt-to-belt difference in multiple belted systems where the multiple belts are supported by the same long rollers. This is the case in the round hay baler.
The continuous high frequency oscillations of the stress/strain loads on the belt in operation are transferred to the points of the belt carcass penetrated by the mechanical fastener. Also, as the belt and the joined belt ends flex about the roller surfaces in a serpentine manner, this movement concentrates considerable stress/strain loads on the joined belt ends through the mechanical fastener due to the differences in belt surface elongations under dynamic loading. This makes it inevitable that the fastened cross-sectional plane of the belt ends can experience uneven stress/strain loads.